Introduction to Binnig and Rohrer's 10 publications,
1981-1986

Gerd Binnig and Heinrich Rohrer submitted their
first publication on the Scanning Tunneling Microscope (STM) in
September 1981. In 1986 they received the Nobel Prize. The following
account describes their publications in this period as a first
guide to the early history of the STM.

What was the nature of their publications in this period? It was
primarily an endeavour to 'sell' the STM. Binnig and Rohrer had
several tasks that fall under the rubric of 'selling', that is to
say: they had to convince their colleagues that their new instrument
was useful. These were the tasks:

show the utility of STM (get interesting results analyzing,
say, the surface of a silicon crystal)

In fact, there were scientists who refused to believe that one could
possibly do what Binnig and Rohrer claimed: to scan a surface yielding
information with a finer resolution than ever before: so fine that
individual atoms showed up. Some scientists thought the STM a hoax
and others accused Binnig and Rohrer with fraud. And so, they had
a very basic task:

convince other scientists that their results were trustworthy

Binnig and Rohrer pursued the first three tasks and through this
they eventually managed to achieve the fourth, basic task. The Nobel
Prize clearly indicates that they had succeeded in convincing the
world at large. It is striking how quickly the recognition came.
Until 1984, noone outside Binnig and Rohrer's lab at IBM Zurich
had replicated an STM experiment. And the first trickle of reports
of replication came from their immediate circle of colleagues, such
as scientists at other IBM labs.
Nonetheless, by 1986 Binnig & Rohrer published an article in Scientific
American and the trickle became a flood. Only a year later,
they received the ultimate recognition. Clearly Binnig & Rohrer's
publications in the period from 1981 to 1986 completed the tasks
in the above list.

The following account asks specific questions that we would like
to have answered. But anyone reading this is invited to respond
in any matter they please. The purpose of this website is to elicit
criticism and to respond to it wherever appropriate. For example,
readers are welcome to criticise the conclusions and the emphases
made. Go to discussions.

The following describes 10 publications by Binnig and
Rohrer between 1981 when they began to publish on tunneling microscopy
and 1986 when they received the Nobel Prize. Very general issues can
be examined using this early STM history. 1981-1986 is an extraordinarily
short time span for 'product development'. One may thus well ponder
such issues as innovation and acceptance of novelty, technology transfer,
and the role of replication and of robustness. The aspiration in the
following pages could be described as preparatory: to get a grip on
the historical development in order to build a solid platform from
which the more general questions may be fruitfully posed.

Binnig and Rohrer's first publication, submitted in 1981, presented
the basic principles of tunneling in a vacuum, particularly that
the tunneling current could be used as a highly sensitive measure
of the miniscule distance between tip and sample. In the following
paragraphs, their argument will be rehearsed. It is well to remember
that they did not simply report

their findings but that they had an interpretation. It was important
for them that other scientists accepted their interpretation and
so they put their best arguments forward. In order to understand
Binnig and Rohrer's endeavour it is necessary also to establish
why other scientists might have been disinterested, sceptic, or
even hostile. Binnig and Rohrer give some clues in this regard in
our interview with them (members may click here),
their Nobel speech, and in Binnig's book, Aus dem Nichts:
'People came to our laboratory and angrily called us liars. We also
received a lot of abusive letters describing us as frauds.' [pp.
128-9]

In almost all their publications in this period, Binnig and Rohrer
had to explain their new tool. And yet, they did not pretend to
completely understand it themselves. For example, in 1984 they stated
that finally the STM had matured from an art to a technique and
that a development from the experimentalist's wishful thinking to
a fundamental theoretical understanding had taken place. One could
call this retrospective modesty as a result of new-found confidence.

Even the basics were contested. The STM works by
scanning a tip across a sample surface, noticing the hills and valleys
in the surface topography. 'Noticing' here refers to a tunneling
current. If the tip is very close to the surface and a small voltage
is applied, then a small current will jump across from sample to
tip (or in the opposite direction). Normally, a current does not
flow through air and so the gap between tip and sample can be regarded
as an insulator. Binnig and Rohrer sometimes carried out the scanning
in a vacuum which is an even better insulator than air. But a current
does flow when the distance between sample and tip is very small,
due to a quantum effect called tunneling. For tunneling to occur,
the distance has to be very small indeed: of atomic dimensions.
This means that you have to be able to position the tip within the
distance of one atom or less from the sample. In fact, the tunneling
current depends not merely on the distance between tip and sample
but rather on the overlap between wavefunctions of the atoms of
tip and sample.

Reproduced from Scientific American,
August 1985, p. 53, by permission of Ian
Worpole.

To many the positioning of an object within the distance
of one atom will have sounded like an impossibility. For much
of the 20th century, quantum mechanics had taught that many
of our common sense notions do not apply at the atomic scale.
For example, the common sense notions related to the mechanics
of billiard balls does not apply. The semi-classical notion
of electrons orbiting the nucleus does not actually apply.
All you can justifiably talk about is wavefunctions (electron
'clouds'), the distribution of which will yield a probability
of finding an electron there upon measurement.

You cannot simultaneously measure with absolute precision the momentum
and position of a particle at the atomic level. And the measurement
(which might involve sending a light particle in to collide with an
electron and then to subsequently detect the scatter) will disturb
the atomic system. In other words, anyone having imbibed quantum mechanics
has learned that common sense notions applied with impunity to macroscopic
phenomena may not be so applied at the atomic level. Hence, the claim
that one could position a tip within a distance of one atom from a
sample and that one can measure a current across such a distance sounded
suspect from the very beginning. And on a more mundane level, thermal
movement, mechanical and acoustical vibrations would render such precision
positioning illusory anyway. Binnig and Rohrer were told that in principle
the STM could not work and their first attempt at publication failed
(Nobel talk, p. 389 and 397). In our interview with the two Nobel
Laureates, much light is thrown on these issues. (Members may clickhere.)
Binnig and Rohrer's attitude to manageability at the atomic level
was unusual. Heinrich Rohrer points to an important lesson of his
PhD work (on length changes of superconductors at the magnetic-field-induced
superconducting transition): that he lost all respect for angstroms
(Nobel talk, p. 387).